Process for producing positive photolithographic printing foils



Jn- 26, 1954 w. NEUGEBAUER ET AL 2,667,415

PROCESS FOR PRODUCING POSITIVE PHOTOLITIIOGRAPIIIC PRINTING FOILS Filed Jan. 13, 1949 \SENSI TIZED. HYDROPHILIC SURFACE] FIG. I

WATER SOLUBLE LAYER \SENSITIZED HYDROPHILIC SURFACE 6 FIG. '.II AcTINlc LIGHT IIIIIIIIIIIIIIII WATER LAYER FIGJII AcTlNlc LIGHT IIIIIIIIIIIIIII INK REPELLANT AREAS I4 INK RECEPTIVE AREAS I6 FIG. 1I

IN VEN TORS @enfin/Lam Hm' u LQ/wpww@ l? j um ATTORNEYS Patented Jan. 26, 1954 PROCESS FOR PRODUCING POSITIVEv PHOTOLITHOGRAPHIC PRINTING FOILS Wilhelm Neugebauer, Wiesbaden-Biebrich, and Jakob Barthenheier, Eddersheim am Main, Germany, assignors, by mesne assignments, to Azoplate Corporation, Summit,-N. J., a corporation of New Jersey Application January 13, 1949, Serial No. 70,803

Claims priority, application Germany October 15, 1948 9 Claims.

This invention relates to a process of producing positive printing foils and plates for flat and offset printing and to new photo-lithographie printing foils which are of use in the neW process.

The pending application for Letters Patent Serial No. 55,228 which Was filed on October 18, 1948, in the name of W. Neugebauer, J. Barthenheier and A. Rebenstock relates to a process of producing negative paper printing foils for lithographic purposes. Photo-sensitive diazo compounds of higher molecular Weight, e. g. condensation products of formaldehyde and the diazo compound of p-amino-diphenylamine, are used in the light sensitive` layer. Also proposals have been made to incorporate diazo compounds of higher molecular Weight, for example, the above mentioned formaldehyde condensation product, into regenerated cellulose which may be used in the form of a foil or in the form of a surface layer on cellulose ester foils. The layer may be formed, for example, by superflcially saponifying the cellulose ester foil. It is essential for the effect, that the base to be sensitized has a hydrophilic surface, and so it is to be understood that polyvinylester foils, e. g. pclyvinylacetate films, also represent a suitable base for the production of -photolithographic printing foils, if they are saponied on their surface.

The light sensitive layer is produced by soaking or brushing the hydrophilic foil withv a solution of the diazo compound. lf foils are photosensitized in this manner, exposed to light under an original, subsequently Washed with Water and then smeared with a fatty ink, the foils take on the fatty ink at all areas which were struck byy the light, i. e. the areas which were not protected by the original, While the foil was being exposed. The areas of the foil which have not been struck by the light repel the fatty ink. Hence, it follows, that the foils just now described are transformed bvy exposure to light under a positive original into a negative printing foil or plate which will produce negative images. By exposure to light under a negative original, a positive printing foil or plate producing positive images is formed.

Diazo compounds suitable for sensitizing the foils are vthe diazo compounds ,of higher molecular weight corresponding with the general formula R-Y-Ar-Ns-X wherein R means an aryl, aralkyl, a higher alkyl or an aroyl residue,

Y means O, S, NH or NR1 R1 standing for alkyl, aralkyl or aryl,

Ar means an aromatic residue, and

X an equivalent of an anion of an acid.

most cases it is advantageous, that the residues R and Ar are substituted by alkoxy, aroxy or N- aryl-sulfamido groups or by one or more halogen atoms. When using a diazo compound of the formula y \N-Ar-N-x as above' defined, the substituents Rand R1 can be Aconnected With one another toform a cyclic compound, or R or R1 can be connected with Ar by a covalent linkage, but it is not'desirable tol have sulfo groups as substituentsin any of R, R1

and Ar.

In order to illustrate the above general formula byfexamples; We' name the diazo compounds of the following amines: 1 amino 4 (Nv ethylbenzyD-aniline, l (N cyclohexyl) aminoaniline, 4- (N-2,6dichlorobenzyl) -amino-aniline, 4',3,6-tribrorn-4-amino-diphenylamine, 4amino 3,6 dimethoxy diphenylamine 2' carboxylic acid, 4-amino-2-sulfamido-(2,5-hydrochinondiethylether) -d'iphenylamine of the formula l amino 4 (benzoyl amino) 2 phenoxy- 5 toloxy benzene, 4 amino 2,5,4 triethoxydiphenylether, 4 amino 2,5 di n propoxy- 4-methyl-diphenylsulde and N-(2,6dichloro benzyl) -3-amino-carbazol.

The diazo compounds, when acted upon with an aldehydeefon: example, drmaldhylenare: transformed-.Sinto condensation productswhich are also suitable for sensitizing the foil.

plied to the light sensitive layer according to the present invention, which are very different from each other. Good results have been obtained with substances such as gum arabic, ce1- 5 lulose ethers, polyuronic acids or their salts,

dextrine, sugar, polyvinyl alcohol, polyvinyl pyrrlflidc'ine:v Watersolubleif;` ureaa resifr'isg protein soluti'ons,-z polyethyleneoxide' pectin substances, sodium alginate, hydrogum, guar resin, poly- Instead of the diaz@ compounds and the aboves 10i-phosphates, e. g. Sodium metaphosphate, and

mentioned aldehyde condensationcproducts theme. selves one may use the sulfonatesitliesefzdiazaf, compounds, which can be prepared in known manner by reaction of the diazo compounds with sulfites. amino compounds can be useciwhich.-are`*p ro,u duced by causing the diazo compundsf'ahdLtlieiiA aldehyde condensation products" respectively to' react with amines following well-described methothers-.. Ifheyfmaytby applied either singly or in combnatinewith each other and/or with other substances;se'.z.rgr.g substances which improve the flexibility of the covers. It may be advantageous,

Furthermore the Q=corrresporrdii-igf diamo-15:5-x-v tofmloosefwateresoluble substances which have a neutralloreweallyracid reaction. Guar resin is denedimthezlournal of the American Chemical Sb'cietmzyolll(1948), pages 2221 and 2222, as polysaccharide (mannogalactan). Hydrogum is ods. Also colorless diazo compoundsmaybemsedg 20k-llthmcommercialinamaiused by the Harris-Seybold Itis the object of our present invent-omisoY modify the above described phcto-sensitiieizl'LY foils, which have a hydrophilic surface containing therein diazo compounds of higher molecular Weight, in such a Way thatthe foil, when exposed to light under a positive original, is converted@ into a p ositive printing rfoil or plate from which.. positive images' can be=produced Ifthe'oilis exposed to light under a negative*original,v a

Companyfor .thamesquite gum which it sells.

Afierthe f'ilhas been exposed to light under an original, and Washed with water in order to remnvaethe Water soluble substance, it is im- 25 portant to squeeze out .the water, immediately,

or.-.to separatazthe-.excessewater pressingathe foilctogether lWithf lterz. paper. `The ..exactness-'Q offlthefprintedwimage is-improved thereby,-

Moreovenwe .haver-foundathatf the.- exactnessoi(l negative :printing fil'f-or plate-fwhich.'produces` 30 thaaimages: and@ prints .Whichrare produced-acnegative images is obtained;v4 Also sa suitable modification ofthe processof exposing'anddevel-' oping thefexposedfoilfmustfbe consideredas'an object,of.;our:-present invention;v

cordingzto-the new Yprocessfcan oftenibeiimproved considerably bye Was-hing printhe expgxsedff; foil'sg; withalsalts solution por. Withfawsolution containing@ substances f Which-.- reduceathe .solubilitysY oitha'..

The invention'.is1illustratedfbygthe accompany- 35- SenStiZng-a'diazozfcompoundf Ori reaCtaWithgthe-.i

ing-pdrawing'imwhichz- Figa/Lisfacviewfimdiagrammaticsectional rele-A vationiof, azlightsensitive `-material ofLthe-.f typedescribed.

Fig,; II .is.a-,view,-in dia'grammaticisectionalselevationrofzthe lightsensitive-materialtcoated with,I

' a-.Awater .solublelayera 1ig.II2[- isIv a-view in diagrammatic sectionalelee'f vation-showing ,the lightsensitivematerial coatedf,

latter 'to form .a.dimcultly.solublacompoun., In...4 this.: connectionewegmention :.e. ...ga aqueousasolue tionsf offlcalciumf, chloride.. ofbetween.. 0.'1;%Jand l.. 0.51% content.,v and-.- aqueousf, solutions.: ofi zinc:v

Excellent efciencyrin thisfrespeetz,iseobtainedi with? substancesawhich possess faiinity.: for;` the.; hydrophilic surface; layer. of the. printing...foil;. Y Very: good results r`are@ obtainable, ion examples-f..

With,the..water.A soluble layer;beingaexposedf.to-A5. With-foils,.consisting of;paper..or.,having.a.cell1,

actinic light,tlslroughamaster.4

lig; IV isaa, `viewin.; diagrammaticl sectional elevation of the plate being completely exposed to actinic light after removal of the Water soluble layer.

The light sensitive-material shown in Fig. I is made up of a base 2 provided with a hydrophilic surface 4, which has been photo-sensitized byrmeansfM ot: one softh'esabcvenneutinediidiazaf: compoundsrfz orf: a; corresponding: dizazosulfonat and diazo amino 'compound respectiyelydsrcoate mthmzewater solubles-layer Esaszshbwneinf-.Figa-I amzlxiriedxv Asshomnzinzlhgcllithegfsensitizedo. hydrophilic surface 4 covered with the .water-er solublelayensexposedito ailightimage'formed (iu:

for., example-:by: placing-,itl rindenafmastell:proe-l vidediwithzopaquefimage areas-@Siam lightz'trans-z mitting-areassif. The Water solubleelayerisf'ree" moye'dbyfmeans :of lwatenand thenth'emateria'l lose-fsur-face,iftheexposed folsiswashed With.a.. dilute.A solution of substantive:salti-likesubstances.` orgsubstantive': dyestuisnassexamples .ofl'wh'ich dyestuffsiweiwish tov disclose:

haveV been.. coated',l ,accordinggt our present-Cim is,.driedfandecompletelyfre:exposedtorlightzwitl es.. vention, with' ayl'm formed 'offyvater 'solublesub' out using-a masteraaszshownrini Figg IV? tofmake 1 the'A areas: fl 6 previously :covered .,by; thef opaque# areas 8 .ofithefma-ster -receptiveetoxgreasyainlc;l The areas I4 exposed to light through the Water stances on: their'` light .sensitive layer' represent ai new kind' lofy lithographic printingfoils which* have. goodffstoringY qualities and Z'oir the advanjtage-` of 'fgiying positive images? from"l ai positive;

soluble layer 6 remain hydrophilicand are ink 7c,.origirial.'

repellant on the press. 'I'he plate ordoil produced in this manner-"When moistened with) Water and smeared with fattyrink, can beiused for producing positive prints.

It 'is'understood,' that'tli new photo-sensitized after the development of the printing foil. Also coating the back surface of the foil with a water insoluble varnish will have the same effect.

In case that a paper sheet is used as base for the production of the printing foil, an advantage may be found in coating the paper sheet with casein and/or a mineral filler before applying the sensitizing solution, the surface of the paper sheet being greatly smoothed thereby.

The following particulars given by way of example, are intended to illustrate our invention:

(1) An aqueous solution containing 3% of the zinc chloride double salt of the condensation product resulting from the reaction of 1 mol. of the sulfate of 4diazodiphenylamine with 1 mol. of paraformaldehyde in sulfuric acid of 60 B., is applied by means of a cotton swab to the surface of a cellulose acetate foil which has been saponified supercially. The excess of the sensitizing solution is removed and the dried foil isuniformly treated with an aqueous protein solu tion, containing 8% of albuminous substance, and dried again. The foil is then exposed to light under a positive original, the exposure being continued until the diazo compounds has faded in the areas not covered by the original. After the exposure of the foil the protein nlm is washed off. Subsequently, the foil is rinsed with an aqueous solution, containing the dyestuff S-iriuslichtblau G, and dried. The dry foil is once more exposed to light, Without an original. When the remaining diazo compound has completely faded, the development is finished and an image has been formed which repels water and takes on fatty inks when moist. If the exposure to light was carried out under a positive original, the prints produced by the printing foil will also be positive.

The same good results are obtained, if in the above described example the specific diazo compound is replaced by another of the diazo compounds, indicated in the description, and/or if the Water soluble film coating is produced by means of other substances stated to be suitable in column 4 of the description. The same holds true with respect to the use of Siriuslichtblau G which can be substituted by the other dyestuffs or salts or salt-like substances mentioned in column 4.

(2) An aqueous solution containing 3% of the sulfonate of the diazo compound of 4-amino-1- N- l2,3,4,6-tetrachlorobenzyll -amino-benzene is brushed on parchment paper and dried. The sensitized surface of the paper foil is treated with a 6% aqueous solution of dextrine, containing 0.8% of phosphoric acid. After drying, the foil is exposed to light and developed, as has been described in Example 1.

The sulfonates of the other diazo compounds, enumerated in the description, and the lmforming water soluble substances, mentioned in column 4, can replace the sulfonate of the diazo compound and the phosphoric acid containing dextrine respectively in the above given example.

(3) An aqueous suspension of the diazo amino compound which is produced from the diazo compound of 4 amino 1 (N2,6dichlorobenzyl) amino-benzene by reaction with guanidine nitrate in a soda solution is brushed on a cellulose acetate foil, which has been saponifled on its surface to a depth of 10u. This sensitive layer is coated With a film which is prepared byspreading on the layer a mixture, composed of 66 ccm. of a 6% aqueous polyvinyl alcohol solution and 34 ccm. of a 12% aqueous dextrine solution, and by immediately drying the coating. The exposure to Subsequently the foil is coated with a 2% aqueous solution of the condensation product prepared from 1 mol. p-diazo-diphenylether, by reaction with l mol. paraformaldehyde in sulfuric acid of 60 B. and rubbed to dryness. The photo-sensitized foil is then brushed with a 6% aqueous solution of dextrine and reciried. Exposureto light and development of the image is the same as described in Example 1.

In the following claims the expression cellulosic foil is intended to designate not only paper, the fibrous material, but also lms which have been produced in known manner fromderivatives of cellulose, for example, cellulose-xanthogenate and cellulose esters, which have been superficially saponied.

What we claim is:

1. The positive working process for producing lithographic printing plates from light sensitive material having a hydrophilic surface which has been photo-sensitized with a diazo compound of high molecular Weight which upon direct exposure to light decomposes into a greasy ink receptive substance, said process comprising the steps of applying an aqueous colloidal solution of Water soluble organic colloid to said sensitized hydrophilic surface to cover said sensi-4 tized surface with a Water soluble organic colloid layer, exposing said sensitized hydrophilic surface provided with said water soluble colloid layer to a light image, removing said water soluble colloid layer and completely reexposing said sensitized hydrophilic surface to light.

2. The positive Working process for producing lithographie printing plates from light sensitive material having a hydrophilic surface which has been photo-sensitized with a diazo compound of high molecular Weight selected from the group consisting `of diazo compounds of the general formula R-Y-Ar-Nz-X wherein R is chosen from aryl, aralkyl, higher alkyl and aroyl residues,

Y is chosen from O, S, NH and NR1, R1 being chosen from alkyl, aralkyl and aryl, Ar is an aromatic residue, and X is an equivalent of an anion of an acid, their aldehyde condensation products, the sulfonates and diazo amino compounds of said diazo compounds and aldehyde condensation products, which process comprises the steps of applying an aqueous colloidal solution of water soluble organic colloid to said sensitized hydrophilic surface to cover said sensitized surface with a Water soluble organic colloid layer, exposing said sen.. sitized hydrophilic surface provided with said Water soluble colloid layer to a light image, removing said water soluble colloid layer and completely reexposing said sensitized hydrophilic surface to light.

3. The positive Working process foi-:,producing lithographie printing plates from light sensitive materialhaving aflxdrophilicfsurface. which has been photo-sensitizedi-Withfa .diazo compound.A of high-molecular weight which upon direct -`exposure-to `light decomposeszinto aggreasy. ink receptive substance, said process comprising the steps of applyingan-aqueous colloidal gumsolution to said sensitized surface with a water soluble colloid gum layer, exposing said sensitized hydrophilic surface provided with said Water soluble colloid gum layer to a light image, removing said Water soluble/,colloid gumlayer and cornpletely reexpcsing said sensitized hydrophilic surface to light.

4. The positive :working process for lproducing lithographie printing vplates froml light sensitive material having a hydrophilicv surface which has been photo-sensitized' with a diazo compound of high Vmolecular weight which upon direct-exposureto light decomposesinto a greasy ink receptive substance, said process comprising the `stepsV o'fv applyingan aqueous, colloidal solution of gum arabic to said sensitized'hydrophilic surface toY cover-saidl sensitized'surface with a Water soluble colloid layer comprising gum arabic, exposing, said sensitized 'hydrophilic surface provided With said Water soluble colloid layer to a light image, removing said water soluble colloid layer andl completely'reexposing said sensitized hydrophilic surface to light.

5. 'I he positive Working -process for producing lithographie vprintingplates from light sensitive materialhaving a hydrophilic surface which has been photo-sensitized Withfa diazo compound of high molecular Weight which. upon direct exposure to lightdecomposesintoj agreasy ink receptive, substance,l said process. comprising the steps of applying'an aqueous. colloidal'solution of mesquite gum tofsaid. sensitized 'hydrophilic surface. to coverpsaid sensitized surface with a Water. solublecolloidr layer A comprising Y mesquite gum, exposing said. sensitized hydrophilicsurface provided with said water solublecolloidvlayer to a light image, removing said yWater .soluble colloid-layerand completely reexposingfsaid sensitized hydrophilic surface to light.r

`6. The positive. Working process forproducing lithographie printing plates fromlight sensitive material. having a hydrophilic surface which has beeny photo-.sensitized with adiazolcompound of material. having s ashydrophilicfsurface; .vvhichghas` been-photo-sensitized with adia-zou compound-tof. high molecular Weight which upondirectnexsposure to light decomposesA into .a greasy inkQreceptive substance, said process comprising the steps 'ofapplying .an aqueous colloidal solution containing poly-vinyL pyrrolidonel to said; sensi;- tized hydrophilicsurface to cover said sensitized surface with a Water .soluble colloid layer comprising polyvinyl pyrrolidone, exposing saidfsensitizedhydrophilic surface, provided with said Water soluble colloidv layer to'. al light. image,fre moving said water soluble colloid layer andfcom.- pletely reexposing.saidasensitizedi hydrophiliczsur face to light.

8. rIhe positive Working process for rproducing lithographie printingplates from light sensitive material having a. hydrophilicsurface Whichfhas been photo -sensitized-i with a; cliazoV compound f of high molecular weight whichupon direct expo,- sure. to. light decomposesv into a igreasyinlrefceptive substance, said process. comprising the steps of lapplying an aqueous colloidal .solution to said sensitized hydrophilic-surface to -cover said sensitized surface with a water soluble. colloid layer comprisingv a substance of the. group consisting of gum arabic, cellulose ethers, poly uronic acids and their salts, dextrine, sugar, polyvinyl alcohol, polyvinyl .pyrrolidina Water soluble urea resins, proteins, polyethylene oxide, pectin substances, sodium alginatemesquitegum and guar resin, exposing said sensitizedhydro.- philic surface provided withsaid; Water-.soluble colloid layer to a light image, removing said Water soluble col-loid layer vand ycompletely reexposing said sensitized hydrophilc'surfaceto light,

9. The positive workingi'processfor producing lithographic printing plateslfrom light sensitive material having a hydrophilic; surface whichhas been photo-sensitizedwith a diazo compound of high molecular Weight which upondire'ct exposure to light decomposes :intoa greasyeinkireceptive substance, said process comprising the steps of applying an aqueoussolution o'f dextrine containing-Sirius lightblue G `to-said sensitized hydrophilic surface to cover'said sensitized surfacewitli-a vWater soluble colloid layerzcomprising dextrine,y exposing said` sensitized hydrophilic surface. provided with said Water soluble. layer toa light image, removing said water Vsolublelayer .by Washing with Water containing Sirius `.light blue C+ and .completely reexposingasaid sensitized hydrophilic surfaceY tolight;

WILHELM .NEUGEBAU'ER J AKOB BARTHENHEIER.

vReferences..Cited the-file of this 'j patent 'UNITED'STATES PATENTS Number Name Date.

v2,312,352 'Tland Mar. 1943 2,316,148 'Bassist Apr'. 1-3, 1943 2,327,380 `T01and Aug.`-24, 1943 2,344,487 Bassist Mar. 271. -1944 

1. THE POSITIVE WORKING PROCESS FOR PRODUCING LITHOGRAPHIC PRINTING PLATES FROM LIGHT SENSITIVE MATERIAL HAVING A HYDROPHILIC SULFACE WHICH HAS BEEN PHOTO-SENSITIZED WITH A DIAZO COMPOUND OF HIGH MOLECULAR WEIGHT WHICH UPON DIRECT EXPOSURE TO LIGHT DECOMPOSES INTO A GREASY INK RECEPTIVE SUBSTANCE, SAID PROCESS COMPRISING THE STEPS OF APPLYING AN AQUEOUS COLLOIDAL SOLUTION OF WATER SOLUBLE ORGANIC COLLOID TO SAID SENSITIZED HYDROPHILIC SURFACE TO COVER SAID SENSITIZED SURFACE WITH A WATER SOLUBLE ORGANIC COLLOID LAYER, EXPOSING SAID SENSITIZED HYDROPHILIC SURFACE PROVIDED WITH SAID WATER SOLUBLE COLLOID LAYER TO A LIGHT IMAGE, REMOVING SAID WATER SOLUBLE SOLLOID LAYER AND COMPLETELY REEXPOSING SAID SENSITIZED HYDROPHILIC SURFACE TO LIGHT. 